I will give it a stab
I don't think LGBT has a single turning point, we are rife with turning points, we make gains only in many cases to end up having quite a bit pulled back. While there are a few things that have gone right in the Federal arena such as DADT, we still do have DOMA. There are only 16 states that protect your rights as a trans person and some are actually explicitly trying to exclude rights, we are actually going backwards in some places.
We will be finished when no person of any orientation, or gender expression has to fear coming out to family, friends, or anyone in public. Because rejections shall cease and so will hate crimes.